1. Field of the Invention
The present invention relates to techniques related to scanning type exposure apparatus and the like; and, in particular, to a scanning type exposure method, apparatus, device manufacturing method, and the like used when manufacturing semiconductor devices, liquid crystal display devices, and the like by lithography process.
2. Related Background Art
Conventionally used in the lithography process for manufacturing semiconductor devices, liquid crystal display devices, and the like are projection exposure apparatus which project and expose, by way of a projection optical system, a pattern formed in a mask or reticle (hereinafter referred to as reticle) onto a substrate such as wafer or glass plate (hereinafter referred to as photosensitive substrate or wafer) coated with photoresist or the like. Of apparatus of this kind, in the main stream have conventionally been stationary type (also known as step-and-repeat system) exposure apparatus which move a wafer stage carrying a wafer as a photosensitive substrate mounted thereon stepwise by a predetermined amount in two-dimensional directions of X and Y, and then transfer a reticle pattern to a shot area on the photosensitive substrate by way of a projection optical system. As the circuit pattern is becoming finer as the semiconductor devices have a higher degree of integration, however, much higher resolution and exposure accuracy have been demanded as performances of the exposure apparatus. Known as an exposure apparatus responding to such a demand are scanning type exposure apparatus of so-called step-and-scan system which sequentially transfer a reticle pattern onto a water by way of a projection optical system by moving a reticle stage holding a reticle and a water stage in a predetermined scanning direction relative to the projection optical system.
Having studied the above-mentioned scanning type exposure apparatus, the inventor has found the following problems. Namely, in the conventional scanning type exposure apparatus, when exposing a reticle pattern onto a certain shot area on a wafer, it is necessary that information (focus information) about the position of the wafer surface along the optical axis direction of the projection optical system (the position indicating the focus state of the exposure area) at the exposure position (within the shot area to be exposed) be measured with a focus sensor immediately before the exposure, and then scanning exposure be carried out while a sample table (z stage) which is minutely movable in the optical axis direction with a wafer held thereby is being positioned such that the shot area surface on the water falls within the depth of focus of the projection optical system.
In such a scanning type exposure apparatus, the focus information of the wafer immediately before starting exposure can easily be detected without any problem in the shot areas other than those located in marginal portions of the wafer. In the case of exposure of a shot area in a marginal portion of the wafer, however, when the wafer surface is displaced along the optical axis direction beyond the trackability of the z stage, a reticle pattern is disadvantageously exposed onto this shot area in a defocused state.
When carrying out exposure while relatively scanning the exposure area conjugate with the illumination area on the reticle from a marginal portion including an edge of the wafer surface to the inside (such an expression being used here for the convenience of explanation though the wafer actually moves while the exposure area is fixed), there has conventionally been employed a method in which exposure is performed while the exposure area is always relatively scanned from the inside of the wafer surface to the marginal portion or a method in which focus sensors to be used are selectively added depending on the position or form of the effective area for exposure shot. In the case where exposure in carried out while relatively scanning from the inside of the wafer surface to the marginal portion, by contrast, though exposure in a defocused state is seen, such a state has been left as it is without no counter measures provided.
In view of such circumstances, it is an object of the present invention to provide aim exposure method, an exposure apparatus, and the like comprising a configuration which can further effectively prevent color inconsistencies from occurring due to defocusing upon exposure.
In order to achieve the above-mentioned object, the exposure method according to the present invention is a scanning type exposure method, as shown in FIG. 5, in which, while a reticle and a substrate are moved relative to each other in a predetermined scanning direction with respect to a projection optical system, a pattern formed in the reticle is sequentially transferred onto the substrate by way of the projection optical system, the method comprising a focus detection stop for detecting positions of a surface of the substrate in an optical axis direction of the projection optical system at a plurality of detection points on the substrate with a multipoint focus sensor; a substrate driving stop of driving the substrate in the optical axis direction of the projection optical system or obliquely with respect to a plane orthogonal to the optical axis; a control step of controlling the driving of the substrate in the substrate driving step; and a judging stop (ST3) for judging, when a sensor in a usable state in the multipoint focus sensor and a predetermined shot area on the substrate have a predetermined relationship with each other, whether the sensor in the usable state is sensible or not; the control step performing, according to a result of the judgment, at least one of a first adjustment operation for adjusting the position of the substrate along the optical axis direction (thickness direction of the substrate) or a second adjustment operation for adjusting the inclination of the substrate.
In this specification, the sensor in a usable state refers to a sensor specified by a user, a sensor used in the immediately preceding scanning exposure step, or the like, which is a sensor, of a sensor group prepared (arranged) beforehand, whose switch is turned on so as to be set to a detection state.
Since the method according to the present invention comprises a judging step for judging whether sensors in the usable state are located within the effective area of the substrate or not, i.e., whether sensible or not, it can be judged whether or not these sensors can be used for controlling the position of the substrate and the like. Further, since the method according to the present invention has an exposure control step, the position of the surface of the substrate and the like can be controlled according to at least one of the first adjustment operation for adjusting the position of the substrate in the optical axis direction (focal position) and the second adjustment operation for adjusting the inclination of the substrate.
Here, it is preferred that the case where the predetermined relationship exists in the judging step be the case where the sensor in the usable state is located at an exposure end position of the predetermined shot area.
As a consequence, when exposure is carried out while the exposure area is relatively scanned from the inside of the wafer surface to a marginal portion including an edge, even upon the exposure of a shot area in the marginal portion, a focusing control operation or a focusing/leveling control operation combining focusing control and leveling control together is appropriately carried out.
In the present invention, the sensor in the usable state may be a follow-up sensor selected in the preceding processing. In this case, the judging step can immediately be carried out without newly selecting a sensor.
As for the adjustment operation determined by the arrangement of sensors, the inclination of the substrate is adjusted with respect to the predetermined scanning direction in the case where the detection points corresponding to the sensors in the usable state include detection points arranged in the predetermined scanning direction. On the other hand, the inclination of the substrate is adjusted with respect to a direction orthogonal to the predetermined scanning direction in the case where the sensors in the usable state include the sensors corresponding to detection points arranged in the direction orthogonal to the predetermined scanning direction. Thus, possible inclination adjustment can be performed according to the arrangement of sensors.
In the judging step, a shot up in which the form of each shot area on the substrate is recorded may be prepared, and the judgment in the judging step may be effected according to the shot map. When the form, arrangement, and the like of each shot area are known beforehand, these items may be stored in the shot map as information and the judgment can be effected by combining this information with the arrangement of sensors in the exposure apparatus used, characteristics of the exposure apparatus such an response speed, and the like.
Another exposure method according to the present invention is an exposure method in which, while a reticle and a substrate are moved relative to each other in a predetermined scanning direction with respect to a projection optical system, a pattern formed in the reticle is sequentially transferred onto the substrate by way of the projection optical system, the method comprising a focus detection step for detecting positions of a surface of the substrate in an optical axis direction of the projection optical system at a plurality of detection points on the substrate with a multipoint focus sensor; a substrate driving step of driving the substrate in the optical axis direction of the projection optical system or obliquely with respect to a plane orthogonal to the optical axis of the projection optical system; a control step of controlling the driving of the substrate in the substrate driving step; a step of preparing a map which specifies a sensible sensor when located at an exposure end position in a predetermined shot area on the substrate; and a step of determining an arrangement of a sensor in a usable state according to the map; the control step performing at least one of a first adjustment operation for adjusting the position of the substrate along the optical axis direction or a second adjustment operation for adjusting the inclination of the substrate, each of which is an adjustment operation determined by the arrangement of the sensor.
In this configuration, for example, when the form and arrangement of each shot area, the arrangement of the exposure apparatus used, characteristics of the exposure apparatus such as response speed, and the like are known beforehand, a map specifying a sensible sensor when located at the exposure end position in a predetermined shot area on the substrate can be prepared according to these data. Further, according to this map, an arrangement of sensors in the usable state can be determined. Then, in the exposure control step, in view of such an arrangement of sensors, one of the adjustment operation for adjusting the position of the substrate along the optical axis direction alone or the adjustment operation for adjusting the inclination of the substrate is performed thus allowing the driving of the substrate to be controlled according to the result of detection in the focus detection step.
The exposure method according to the present invention may include an automatic selection step of changing the arrangement of sensors in the usable state according to the result of the judging step.
In this method, at the automatic 9 election step, focus sensors fulfilling a predetermined standard may be selected according to a predetermined order.
In such a configuration, when the predetermined standard is defined as the most inside and outside of the first row, for example, width covered by sensors can be made greater, thus enhancing the possibility of leveling. Also, when the predetermined order is determined such that, for example, the sensors contributing to leveling are selected earlier than those simply contributing to focusing, the leveling that has conventionally been abandoned can be carried out as well.
The exposure apparatus according to the present invention is as shown in FIG. 1, an exposure apparatus 100 which, while scanning a reticle R and a wafer W in synchronization with each other, transfers a pattern of the reticle R to a shot area IA (FIG. 2) on the wafer W by way of a projection optical system PL; the apparatus comprising a focus detection system 40, 42 for detecting positions of the wafer W in the direction of an optical axis AX of the projection optical system at a plurality of detection points on the wafer W with a plurality of focus sensors S12 to S53 (FIG. 3) set; a driving mechanism 21 for driving the wafer W in the direction of the optical axis AX or obliquely with respect to a plans orthogonal to the optical axis AX; a judging section for detecting whether the focus sensors are sensible or not according to a positional relationship between the focus sensors, the wafer, and the shot area; and a control system for controlling scanning exposure in the shot area.
In this case, the control system may be configured such as to adjust, according to the result of judgment by the judging section, at least one of the position of the wafer in the direction along the optical axis AX and the inclination of the wafer.
In the present invention, the control system may be configured such as to change the setting of the focus sensors according to the form of a shot area located in a marginal portion including an edge of the wafer.
In the present invention, the control system may be configured such as to change the setting of the focus sensors according to the difference in length between both ends of the shot area in the scanning direction.
The device manufacturing method according to the present invention is a device manufacturing method in which, while a reticle and a wafer are scanned in synchronization with each other, a pattern of the reticle is transferred to a shot area on the wafer, so as to make a semiconductor device on the wafer; the method comprising the steps of detecting focus positions at a plurality of detection points on the substrate with a plurality of focus sensors and driving the substrate into a focusing direction or obliquely driving the substrate surface; judging whether the focus sensors are sensible or not according to a positional relationship between the focus sensors, the substrate, and the shot area; adjusting at least one of the position of the substrate in the optical axis direction and the inclination of the substrate with the focus sensors determined according to a result of the judgment; and exposing the pattern of the reticle onto the adjusted substrate.
As a consequence, in a marginal area of the substrate, for example, focus control or leveling control is appropriately effected as much as possible, whereby devices such as those of semiconductor and the like can be manufactured while satisfying both exposure accuracy and throughput as a whole.
In the present invention, the control system can effect scanning exposure according to not only the positional relationship between the substrate and the detection area but also the positional relationship between shot areas on the substrate, and the positional relationship between a shot area an the substrate and an edge of the substrate.
Specifically, the judging section judges a first condition that the distance from a shot area in which scanning exposure has been completed to the next shot area, to be subjected to scanning exposure in at least a predetermined value, and a second condition that a detection point, included within the detection area, corresponding to a sensor in the usable state intersects an edge of the substrate as the substrate moves. According to the result of this judgment, the control system performs a predetermined scanning exposure operation. For example, when both of the first and second conditions are satisfied, at least one of first and second control operations is selectively carried out.
Preferably, the positional relationship between a shot area on the substrate and an edge of the substrate is given by the distance between an exposure start position or exposure and position in a predetermined shot area on the substrate and the edge.
Namely, when satisfied is the first condition that the distance from the exposure start position in the shot area to the edge of the substrate along the scanning direction is at least a first value while at least three of the plurality of detection points exist on the substrate at the time of starting exposure, the control system carries out the first and second adjustment operations. When satisfied is the second condition that the distance from the exposure start position in the shot area to the edge of the substrate along the scanning direction is lose than the first value but at least a second value smaller than the first value while, of detection points arranged on a line orthogonal to the scanning direction and located on the substrate, detection points at both ends are separated from each other by at least a predetermined distance, the control system carries out the first and second adjustment operations. When neither of the first and second conditions is satisfied, the control system carries out only the first adjustment operation.
On the other hand, when satisfied is a third condition that the distance from the exposure end position in the shot area to the edge of the substrate along the scanning direction is at least a third value while at least three of the plurality of detection points exist on the substrate at the time of terminating exposure, the control system carries out the first and second adjustment operations. When satisfied is a fourth condition that the distance from the exposure end position in the shot area to the edge of the substrate along the scanning direction is less than the third value but at least a fourth value smaller than the third value while, of detection points arranged on a line orthogonal to the scanning direction and located on the substrate, detection points at both ends are separated from each other by at least a predetermined distance, the control system carries out the first and second adjustment operations. When neither of the third and fourth conditions is satisfied, the control system carries out only the first adjustment operation.
The present invention may further comprise a plurality of sensors respectively corresponding to a plurality of detection points included within a detection area of the focus detection system; and a sensor selecting mechanism for selecting, of the plurality of sensors, a sensor used for adjusting the position of the substrate by the control system. Here by way of the sensor selecting mechanism, the control system selects a sensor located on the substrate at an exposure start position or exposure end position among the plurality of detection points.
More preferably , upon scanning exposure of the shot area on the substrate, the control system carries out at least one of the first operation for adjusting the position of the substrate in the thickness direction and the second adjustment operation for adjusting the inclination of the substrate according to detection information obtained from the focus detection system, and information obtained upon immediately preceding scanning exposure.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.